This application is based on and claims the priority under 35 U.S.C. xc2xa7119 of German Patent Application 198 57 891.1, filed on Dec. 15, 1998, the entire disclosure of which is incorporated herein by reference.
The invention relates to a crawler or tracked vehicle having a running gear with separately operable tracks, a vehicle body arranged generally above the running gear, and at least one tool.
Crawlers or tracked vehicles, also commonly known as caterpillar vehicles or smaller xe2x80x9cskid-trackxe2x80x9d vehicles, have been used for a long time and are well known in the art. They are generally equipped with at least one tool such as a dozer blade, a bucket loader, a backhoe or digging bucket, a trencher, forestry equipment, a lifting crane, or the like. They are primarily used as construction or earth-moving vehicles at construction sites, and their primary applications lie in transmitting large forces to the ground and being able to operate on uneven or rough terrain. Such crawler vehicles are also used as military transport and battle vehicles, and as transport or work vehicles on snowy and icy terrains.
Conventionally in such crawler vehicles, the running gear including the crawler tracks is rigidly mounted with respect to the vehicle body. As a result, one of the difficulties of operating such a crawler vehicle is that the tilting motions of the running gear and particularly of the crawler tracks, arising from moving over uneven or rough terrain, are also transmitted directly to the body of the vehicle and thus to the operator. Thereby the operator is subjected to tilting movements that may cause discomfort and may present an unsafe operating condition. Moreover, if the entire vehicle body is forced to tilt with the tilting of the crawler tracks, then the vehicle may become unstable and likely to tip over when operating on very rough or uneven terrain. The conventional crawler vehicle also suffers a limitation on the degree of unevenness or roughness that it can traverse, because the two crawler tracks are not able to tilt independently. Thus, conventional crawlers are not well suited for operating on terrain that is irregularly uneven in two or three dimensions, e.g. with a different direction of slope of the ground under each of the two crawler tracks.
In view of the above, it is an object of the invention to provide a crawler or tracked vehicle and especially a so-called skid-track vehicle that is so designed that the tilting movements of the crawler tracks resulting from traveling over uneven or rough terrain are significantly reduced and/or damped before they are passed on to the vehicle body. In other words, it is an object of the invention to substantially isolate the vehicle body from the tilting movements of the running gear and particularly the crawler tracks. The invention further aims to avoid or overcome the disadvantages of the prior art and to achieve advantages as are apparent from the present specification.
The above objects have been achieved according to the invention in a crawler or tracked vehicle having a running gear with separately operable tracks, and a vehicle body that is pivotably connected to the running gear so as to be pivotable about at least one pivot axis. Preferably the pivot axis is substantially horizontal (e.g. within +/xe2x88x925 degrees of horizontal when the crawler is standing on level horizontal ground). More particularly the pivot axis is preferably parallel to the rotation axes of track deflection wheels of the crawler track arrangements.
The crawler vehicle according to the invention includes at least one pivot axle that physically pivotably connects the vehicle body with the running gear and defines the above mentioned at least one pivot axis. Preferably two respective pivot axles independently connect the vehicle body with the two respective crawler track arrangements of the running gear, so that each crawler track arrangement is tiltable independently of the other and independently of the vehicle body. The crawler vehicle further includes at least one spring arrangement that is arranged at a distance from the pivot axis and that elastically connects the running gear and the vehicle body. The spring arrangement allows the running gear to pivot and tilt with some freedom of movement relative to the vehicle body and attenuates and/or delays the transmission of some of the tilting movements from the running gear to the vehicle body.
The spring arrangement comprises a respective helical spring preferably arranged on each side of the vehicle body, whereby these helical springs can be arranged substantially vertically or substantially horizontally. In this context, xe2x80x9csubstantially verticallyxe2x80x9d means within +/xe2x88x9210 degrees of true vertical, and xe2x80x9csubstantially horizontallyxe2x80x9d means within +/xe2x88x9210 degrees of true horizontal, when the crawler vehicle is standing on level horizontal ground. One end of each helical spring is connected to the frame of the vehicle body and the other end thereof is connected to a respective one of the crawler track arrangements of the running gear. The spring arrangement preferably further comprises a hydraulic or pneumatic damper device, such as any conventional shock absorber, arranged in parallel with each helical spring to damp out the relative tilting or pivoting movements between the crawler track arrangements and the vehicle body.